1. Field of the Invention
This invention relates to a method and an apparatus for joining a plurality of flat-plate electrodes adapted to, e.g., a flat type display unit while spacing the electrodes from each other by a predetermined small distance.
2. Description of the Prior Art
Conventionally, flat-plate electrodes for use in a flat type display unit are joined to each other as described below. Referring to FIG. 3, spacers 32 having two major surfaces to which a glass frit 33 of a low-melting-point bonding glass is applied are interposed between a plurality of flat-plate electrodes 31, that is, the flat-plate electrodes 31 and the spacers 32 are alternately superposed on each other. This stack of the flat-plate electrodes and the spacers 32 is placed on a firing base plate 34, and a stamper 35 is placed on the stack to impose a constant load on the same. In this state, these members are inserted into a firing furnace 36 and are heated at a temperature equal to or higher than a predetermined temperature to melt the glass frit 33, thereby joining the flat-plate electrodes 31 while interposing the spacers 32 therebetween. In FIG. 3, numeral 37 denotes a fan serving to make the heating temperature in the furnace uniform. Numeral 36 denotes positioning pins provided to position the flat-plate electrodes 31 and the spacers 32 relative to each other.
This joining method includes the steps of increasing the temperature in the furnace after inserting the members into the furnace, maintaining the furnace temperature at the set point for a predetermined period of time, reducing the furnace temperature and thereafter removing the members. Therefore the time taken for the joining process is long and the productivity is considerably low. There is a risk of extraneous substances attaching to the electrodes because the furnace atmosphere is agitated by the fan in order to make the furnace temperature uniform. Moreover, even if the constant load is uniformly applied to the electrodes and the spacers by means of a stamper, a problem of difficulty in improving the joining accuracy with respect to the degree of parallelism and the spacing between the flat-plate electrodes is encountered because of dispersion of the heating temperature distribution, dispersion of the glass frit composition, non-uniformity of the applied state of the glass frit, and so on.